This invention relates to a floating head slider used in a magnetic storage device.
Many magnetic disc recording devices with a so-called "hard disc" as the recording medium are in use as large capacity storage devices in information processing systems. In these devices, the high speed magnetic recording and reproduction of information is effected by causing the hard disc to rotate at high speed and having a magnetic head on a floating head slider face the information recording surface of this disc with a microgap therebetween.
FIG. 1 shows a conventional floating head slider as described in U.S. Pat. No. 3,823,416. Two bearing surface 3 and 3' parallel to each other are formed on the underside of the floating head slider 1. A projecting magnetic head 5, its lower tip constituting a recording/reproducing part 6, is mounted on the underside between surfaces 3 and 3'. Tapering surfaces 7 and 7', constituting a kind of pressure-raising mechanism for the air in flow along surfaces 3 and 3', are formed on one end of each of the above-mentioned bearing surfaces 3 and 3'. This kind of floating head slider 1 is in practice supported in the manner illustrated in FIG. 2. As this floating head slider in FIG. 2 faces the underside of the disc 8 which constitutes the storage medium, the direction in which it is facing is in fact the opposite of that in FIG. 1. In FIG. 2, the floating head slider 1 is supported by a set of gimbals 10 which is itself supported by a mounting arm 9, and is thrust by a leaf spring 11 (integral with the gimbals 10) in the direction required for pressure contact with disc 8.
When disc 8 is stationary, floating head slider 1 touches the surface of the disc and when disc 8 starts to rotate, the tapering surfaces 7 and 7' which constitute the pressure-raising mechanism cause it to separate from the disc, i.e. to float, as shown in FIG. 3(a). Under these conditions the pressure distribution pattern along the bearing surfaces 3 and 3' is as indicated in FIG. 4(b). The application to the point of support 12 of the floating head slider 1 by leaf spring 11 of a thrust equivalent to the integral of the generated pressure shown in FIG. 3(b) causes the gap between the recording/reproducing part 6 of the floating head slider 1 and the surface 8a of the disc 8 to be kept constant. This gap between the recording/reproducting part 6 of the floating head slider 1 and the surface 8a of the disc is highly important in achieving stable recording and reproduction characteristics.
In order to achieve good recording quality by improving the tracking of the floating head slider 1 of the disc 8, it is best to make the above mentioned gap narrow. However, if a large thrust is applied to the magnetic head slider so as to narrow the gap, the friction between the bearing surfaces 3 and 3' of the magnetic head slider 1 and the surface 8a of the disc 8 during low speed running (when the disc 8 is being started or stopped) is intensified, resulting in increased abrasion of the surfaces 3 and 3' and therefore shortening the life of the magnetic storage device.
One way of eliminating this drawback is not to apply the thrust to the floating head slider 1 when the disc 8 is running at low speed, and to apply it only when the speed is above a certain value. However, a mechanism to effect this is expensive, and the risk exists of the bearing surfaces 3 and 3' of the slider 1 colliding with the surface 8a of the disc 8 when the floating head slider 1 is brought closer to the disc 8 during running. This solution, therefore, is not really practicable.
Other possible solutions are to provide, as illustrated in FIG. 4, and shown in U.S. Pat. No. 3,855,625 tapered recesses 13 in the central area of the underside of the floating head slider 1a, or, as shown in FIG. 5, stepped recesses 14 at the air outflow end of the central area of slider 1b, to lessen the frictional abrasion between the bearing surfaces 3 and 3' of the floating head sliders 1a and 1b and the surface 8a of the disc 8 when the disc is starting or stopping by causing negative pressure to be generated during running, and so applying a reduced thrust.
However, the provision of a tapered recess or a stepped recess requires additional processing, and therefore increases the cost of manufacture.